Method for manufacturing a floor carpet structure including a sensing function for an automotive vehicle

ABSTRACT

A method for manufacturing a floor carpet structure including a sensing function for an automotive vehicle, comprises the steps of providing an upper carpet laminate ( 4, 5 ) with at least one fibrous layer ( 4 ), providing a separate sensing device ( 1 ), and embedding said sensing device ( 1 ) into said carpet structure by applying a rear reinforcement structure ( 6 ) to a lower surface of said upper carpet laminate ( 4, 5 ).

INTRODUCTION

The present invention generally relates to a method for fitting asensing device into a foot compartment of an automotive vehicle.

In order to protect the lives of passengers during a traffic accident,modern vehicles are generally provided with a protection systemcomprising several airbags and seat belt pretensioners, which are usedto absorb the energy of a passenger released during the collision due tothe accident. It is clear that such protection systems are mosteffective when they are well adapted to the specific requirements of anactual seat occupancy. That is why microprocessor-controlled protectionsystems have been designed which provide several operational modes,allowing for example an adaptation of the instant at which airbags aredeployed, the volume to which the airbags are inflated, the instant atwhich safety belts are released after the collision, etc, as a functionof the stature of a passenger on the seat. In order to enable thecontrol microprocessor to select the optimum operational mode for agiven seat occupancy status, it is of course necessary to detect one orseveral parameters characterizing the occupancy status of the seat andto classify the occupancy into one of several classes, each of which isassociated to a specific operational mode of the restraint system.

One approach for gathering relevant parameters of a seat occupancy isbased on the detection of the capacitive coupling of a body to one orseveral electrodes arranged in the seat. Such a measurement system isfor instance described in LU-A-88 828. This measurement system comprisesat least one transmitting electrode and at least one receiving electrodethat are capacitively coupled by a conductive body. The receivingelectrodes are connected to an analysis circuit that determines thecapacitive coupling of the transmitting antenna with the conductive bodyby comparing the measured signal with a reference signal.

Various other systems have been disclosed with electrodes arranged atdifferent locations in the passenger compartment in order to detect thepresence and/or the nature of a seat occupancy and to classify theoccupancy status in one of several classes. German patent applicationDE-A-102 35 881 discloses e.g. a combined occupant detection systemcomprising a first electrode arranged in a seating surface of a vehicleseat and a second electrode arranged in the foot compartment of thevehicle. The combined detection system can further comprise a pressuresensitive mat to be arranged together with the second electrode into thefoot compartment.

In modern automotive vehicles, the foot compartment is no longer simplycomposed by a metal sheet covered with a simple carpet layer. The footcompartment has rather become a sophisticated environment where a numberof technical components of the vehicle, like e.g. air conditioningtubes, cables, noise absorbers, etc., are integrated and covered by athree-dimensionally formed carpet structure. The vehicle carpetstructure itself has to fulfil a number of functions such as providingnoise absorption, water resistance, flame protection etc. For thisreason, the vehicle carpet is typically manufactured by providing anupper, three-dimensionally moulded carpet laminate with a rearreinforcement structure of a synthetic foam material, whereby thereinforcement structure is shaped so as to conform to the vehicle shellcontour and the technical components arranged thereon.

It is clear that the integration of further sensing devices into such anenvironment has to meet a number of requirements, especially if thesensing device itself should be protected against outer environmentalinfluences and high mechanical stress. A solution must thus be found tointroduce a large surface sensor device into the foot compartment.

French patent application FR-A-2 595 441 discloses a security devicecomprising a carpet, which is configured as a contact sensor fordelivering an electrical signal in response to pressure acting on thecarpet. The carpet is made of a soft felt material, wherein at least apart of the fibres forming the felt material are made of electricallyconducting material. It will be clear that this solution is not suitablefor meeting the above-mentioned requirements.

OBJECT OF THE INVENTION

The object of the present invention is accordingly to provide animproved method for integrating a sensing device into the carpetstructure of a vehicle foot compartment.

GENERAL DESCRIPTION OF THE INVENTION

This object is achieved by a method for manufacturing a floor carpetstructure including a sensing function for an automotive vehicleaccording to claim 1. This method for manufacturing a floor carpetstructure including a sensing function for an automotive vehicle,comprises the steps of providing an upper carpet laminate, said carpetlaminate comprising at least one fibrous layer; providing a separatesensing device; and embedding said sensing device into said carpetstructure by applying a rear reinforcement structure to a lower surfaceof said upper carpet laminate. According to the present invention, aseparately provided sensing device is securely embedded within thecarpet structure. As a result, the sensing device is protected by thedifferent layers of the carpet structure from all kinds of outsideenvironmental conditions such as moisture and the like and effectivelyelectrically isolated from the vehicle body. Furthermore, the uppercarpet laminate, which is usually made of several layers providing ahigh mechanical resistance and shock absorption, reduces the mechanicalstress acting on the sensing device and prevents the sensing device frombeing destroyed due to very high localized loads such as the loadexerted by stiletto heels or the like. The method of the presentinvention accordingly secures the sensing device in a location, whichoffers best protection against all kinds of environmental influences.

Furthermore, the embedding of the sensing device into the carpetstructure advantageously geometrically secures the sensing device to itsoperating position inside the carpet structure and thus prevents thesensing device from being displaced once the reinforcement structure isapplied. As a result, no further undesired sensor dislocation ispossible and accordingly no additional position adjustment will berequired.

In a first embodiment of the invention, the sensing device is foamedinto the reinforcement structure itself. In this embodiment, the step ofembedding includes the steps of arranging said sensing device at acertain distance below said lower surface of said upper carpet laminateand foaming said reinforcement structure onto said lower surface,thereby embedding said sensing device into said reinforcement structure.However in a preferred embodiment, the sensing device should be embeddedinto the carpet structure between the upper carpet laminate and the rearreinforcement structure. In this embodiment, the step of embeddingcomprises the steps of securing the sensing element to said lowersurface of said upper carpet laminate, and applying said a rearreinforcement structure to said lower surface of said upper carpetlaminate and said sensing device secured onto said lower surface. Thelatter embodiment does not require sophisticated supporting means forarranging the sensing device at a certain distance below the uppercarpet laminate. Instead, the sensing device is simply fastened directlyto the lower surface of the upper carpet laminate by any possible means.The sensing device may e.g. be adhesively bonded by means of adhesivetape or mechanically by some sort of Velcro fasteners. Alternatively thesending device could be fastened using magnetic or electrostaticattraction or by mechanical fitting means.

The rear reinforcement structure may be adhesively bonded to the uppercarpet laminate. However in a preferred embodiment, the rearreinforcement structure is directly formed onto the lower surface of theupper carpet laminate by a foaming process. This means that the step ofapplying said a rear reinforcement structure to said lower surface ofsaid upper carpet laminate comprises the step of foaming saidreinforcement structure onto said lower surface. The foaming process iswell suited for securely integrating and positioning the sensing deviceinto the carpet structure at low costs and meets all the requirementsfor high volume production.

It will be appreciated, that the foaming process also enables an easyintegration of an electrical connection line for connecting the sensingelement to a control unit. The connection line may simply be foamed intothe reinforcement structure so as to exit on a lateral or lower surfacethereof. The connection line may also be arranged inside plastic filmcontainer, which extends to a lateral or lower surface of thereinforcement structure. This plastic film container may then be openedthe foaming process so as to give access to the connection line.

It will be noted that the upper carpet laminate preferably comprises atleast one heavy layer and/or at least one felt layer bonded to saidfibrous layer for improving the laminates shock and noise absorbingproperties. These different layers are preferably laminated togetherprior to securing said sensing device onto said carpet laminate.

The upper carpet laminate is preferably moulded into a three-dimensionalstructure prior to the application of said a rear reinforcementstructure. This provides the advantage that the carpet structure doesnot require further extensive forming after the integration of thesensing device, which avoids that the and accordingly the sensing devicewill not be subjected to later mechanical bending stress.

It will be appreciated that the present invention proposes a methodwhich is suitable for the integration of various types of sensingdevices in the carpet structure of a vehicle. Possible embodiments ofsuch a sensing device includes a pressure sensing mats, such as afoil-type pressure sensing mat made of force sensing resistors, or asheet electrode of a metal foil or conductive (woven or non-woven)textile for capacitive sensing systems.

DETAILED DESCRIPTION WITH RESPECT TO THE FIGURES

The present invention will be more apparent from the followingdescription of a not limiting embodiment with reference to the attachedFIG. 1, which illustrates the different elements of a carpet structurewith integrated sensing device.

The carpet structure 10 shown in FIG. 1 generally comprises a fibrouslayer 4 and a heavy layer 5 laminated together to form an upper carpetlaminate. The fibrous layer comprises e.g. a number of fibres or yarntufts anchored in a table backing material. The heavy layer may bemanufactured of a fleece, non-woven of felt layer and mostly serves as anoise absorber. The upper carpet laminate is e.g. manufactured in astamping process, where the heavy layer 5 is melted to the fibrous layer4 and the so formed laminate is subsequently moulded into its final 3Dgeometry.

A sensing device 1, e.g. a capacitive electrode made of any suitableconductive sheet material 2 is then secured to the lower surface of theupper carpet laminate e.g. by means of an adhesive tape or Velcrofasteners or the like 3. The sensing device comprises a connection line12 for connecting the sensing device 1 to an external control unit 14.The connection line 12 may also be fastened to the upper carpetlaminate, e.g. inside a plastic foil container.

Once the sensing device is arranged at the predetermined location, arear reinforcing structure 6 is applied onto the rear surface of theupper carpet laminate by a foaming process. The reinforcement structurethus tightly encases cases the sensing device 1 so that the sensingdevice 1 will be integrated in an entirely protected location. It willbe noted that the lower surface of said reinforcement structure isshaped so as to conform to a vehicle shell contour and possibly totechnical components arranged thereon.

LIST OF REFERENCE NUMERALS

-   1 sensing device 6 reinforcing structure-   2 conductive sheet material 10 carpet structure-   3 fasteners for sensor 12 connection line-   4 fibrous layer 14 external control unit-   5 heavy layer

1. Method for manufacturing a floor carpet structure including a sensingfunction for an automotive vehicle, said floor carpet structurecomprising an upper carpet laminate and a rear reinforcement structure,said method comprising the steps of providing said upper carpetlaminate, said carpet laminate comprising at least one fibrous layer;providing a separate sensing device; arranging said sensing device withrespect to a lower surface of said upper carpet laminate; and embeddingsaid sensing device into said carpet structure by applying said rearreinforcement structure to said lower surface of said upper carpetlaminate.
 2. Method according to claim 1, wherein said step of arrangingsaid sensing device with respect to said lower surface of said uppercarpet laminate comprises the step of arranging said sensing devicebelow said lower surface of said upper carpet laminate and wherein saidstep of embedding includes the step of foaming said reinforcementstructure onto said lower surface, thereby embedding said sensing deviceinto said reinforcement structure.
 3. Method according to claim 1,wherein said step of arranging said sensing device with respect to saidlower surface of said upper carpet laminate comprises the step ofsecuring the sensing element to said lower surface of said upper carpetlaminate and wherein said step of embedding comprises the step ofapplying said rear reinforcement structure to said lower surface of saidupper carpet laminate and said sensing device secured onto said lowersurface.
 4. Method according to claim 1, wherein said step of applyingsaid rear reinforcement structure to said lower surface of said uppercarpet laminate comprises the step of foaming said reinforcementstructure onto said lower surface.
 5. Method according to claim 1,wherein said upper carpet laminate comprises at least one heavy layerand/or at least one felt layer bonded to said fibrous layer.
 6. Methodaccording to claim 1, wherein said upper carpet laminate is moulded intoa three-dimensional structure prior to the application of said a rearreinforcement structure.
 7. Method according to claim 1, wherein saidsensing device comprises a pressure sensing mat.
 8. Method according toclaim 1, wherein said sensing device comprises a sheet electrode.